On-demand Geographic Forwarding for data delivery in wireless sensor networks

A purely on-demand network protocol, called On-demand Geographic Forwarding (OGF), is proposed for data delivery in large-scale and resource-constrained static wireless sensor networks with unreliable sensors. OGF is a cross-layer protocol that employs (i) an explicit contention scheme to establish a next-hop node in a distributed fashion, (ii) a simple scheme using a forwarding table to maintain the learned next-hop information, and (iii) a novel partial source routing scheme to handle communication voids. The operation of our protocol is based on the actual demands of the application, data traffic, and network dynamics. Packet-level simulations show that OGF exhibits a superior performance in terms of energy consumption, scalability, and void handling. Our study demonstrates that OGF is viable for efficient data delivery in the targeted sensor networks.     

Autonomic Application-Level Message Delivery Using Virtual Magnetic Fields

Mobility has emerged as an important new trend in the arena of distributed computing bringing along deep social and technical transformations. These changes have created an increasing demand for applications and middleware that exploit and support mobility. This article proposes the use of the concept of magnetic fields borrowed from physics to enable self-organizing message forwarding on overlay networks over physical networks with possibly mobile nodes. Though autonomic, a network that employs the proposed message forwarding mechanism still needs a cognitive management to accomplish end-to-end goals. After formalizing the generic model of virtual magnetic fields, a distributed self-stabilizing propagation algorithm is defined and applied to the load-balancing problem. Simulation results are then discussed and implementation issues are detailed considering extensions of existing platforms. At last, conclusions are drawn and the main future works are listed.     

Energy efficient and reliable data delivery in urban sensing applications: A performance analysis

Urban sensing is an emerging application field for Wireless Sensor Networks (WSNs), where a number of static sensors is sparsely deployed in an urban area to collect environmental information. Data sensed by each sensor are, then, opportunistically transmitted to Mobile Nodes (MNs) that happen to be in contact. In the considered scenario, communications between MNs and sensors require paradigms with a minimal synchronization between devices, extremely fast and energy efficient, especially at the sensor side. To deal with the above issues, in [1] we proposed a hybrid protocol for data delivery from sensors to MNs, named Hybrid Adaptive Interleaved Data Protocol (HI). By combining Erasure Coding (EC) with an Automatic Repeat reQuest (ARQ) scheme, the proposed protocol maximizes the reliability of communications while minimizing the energy consumed by sensors. In this paper, we present an in-depth analysis of the HI performance. We provide an analytical evaluation by defining a flexible model to derive the probability of data delivery and exploiting it to investigate the performance over a wide range of parameters. Moreover, we perform an experimental study to evaluate the HI effectiveness on real sensor platforms. Specifically, we analyze the impact of resource constraints imposed by sensors on data delivery and provide a careful characterization of its actual consumption of resources.     

An energy-efficient,transport-controlled MAC protocol for wireless sensor networks

In wireless sensor networks (WSNs), one major cause of wasted energy is that the wireless network interface is always on to accept possible traffic. Many medium access control (MAC) protocols therefore adopted a periodic listen-and-sleep scheme to save energy, at sacrifice of end-to-end latency and throughput. Another cause is packet dropping due to network congestion, necessitating a lightweight transport protocol for WSNs. In this paper, we suggest a transport-controlled MAC protocol (TC-MAC) that combines the transport protocol into the MAC protocol with the aims of achieving high performance as well as energy efficiency in multi-hop forwarding. Although TC-MAC also works through a periodic listen-and-sleep scheme, it lowers end-to-end latency by reserving data forwarding schedules across multi-hop nodes during the listen period and by forwarding data during the sleep period, all while increasing throughput by piggybacking the subsequent data forwarding schedule on current data transmissions and forwarding data consecutively. In addition, TC-MAC gives a fairness-aware lightweight transport control mechanism based on benefits of using the MAC-layer information. The results show that TC-MAC performs as well as an 802.11-like MAC in end-to-end latency and throughput, and is more efficient than S-MAC in energy consumption, with the additional advantage of supporting fairness-aware congestion control.     

基于虚拟力的混合感知网节点部署

感知网一般是由静态的或移动的节点组成,为保证感知网的感知功能,节点应该有自部署和自修复能力.然而全部由移动传感器组成的感知网的成本太高,为保证感知网的覆盖功能和低成本,提出了一种在静态传感器节点中加入移动传感器节点的混合感知网形式.为了更好地部署这些节点,最大化覆盖待感知区域,提出了一种基于节点间虚拟力的移动节点部署方法,利用静态节点和移动节点以及移动节点之间的虚拟人工势场产生的作用力来控制移动节点的运动,使移动节点能够在较短的时间内,以较少的能量消耗到达自己合适的位置.在理论上分析了算法的可行性,用仿真实验验证了此算法的有效性,并和其他3种类似算法进行了性能比较.     

移动互联网可信匿名通信模型

针对移动互联网对通信过程的匿名性需求,提出基于签密和可信计算技术设计移动互联网下的匿名通信模型,以实现通信双方间的匿名通信。该模型中,中间节点根据前驱节点的签密信息鉴别转发数据的完整性,验证转发链路的真实性。分析表明该模型在实现通信匿名的同时具有安全性与可信性,满足移动互联网下移动终端匿名通信过程的安全需求。     

An enhanced real-time routing protocol with load distribution for mobile wireless sensor networks

Mobile wireless sensor network (MWSN) is a wireless ad hoc network that consists of a very large number of tiny sensor nodes communicating with each other in which sensor nodes are either equipped with motors for active mobility or attached to mobile objects for passive mobility. A real-time routing protocol for MWSN is an exciting area of research because messages in the network are delivered according to their end-to-end deadlines (packet lifetime) while sensor nodes are mobile. This paper proposes an enhanced real-time with load distribution (ERTLD) routing protocol for MWSN which is based on our previous routing protocol RTLD. ERTLD utilized corona mechanism and optimal forwarding metrics to forward the data packet in MWSN. It computes the optimal forwarding node based on RSSI, remaining battery level of sensor nodes and packet delay over one-hop. ERTLD ensures high packet delivery ratio and experiences minimum end-to-end delay in WSN and MWSN compared to baseline routing protocol. In this paper we consider a highly dynamic wireless sensor network system in which the sensor nodes and the base station (sink) are mobile. ERTLD has been successfully studied and verified through simulation experiment.     

AVP: A Highly Efficient Transport Protocol for Low Bit Rate Multimedia Communications

Utilization of Internet communications in distance learning, distributed simulation, and distributed work groups involves multimedia transmission of animation, voice and video clips. Highly compressed audio-video data protocols are required for efficient Internet multimedia communications. Addressing this requirement, a new transport protocol called Audio-Video Protocol (AVP) for highly efficient multimedia communications on the Internet is presented. While providing similar real-time delivery functions as Real-Time Transport Protocol (RTP) and Real-Time Control Protocol (RTCP), AVP adopts a novel audio-based synchronization scheme. This synchronization scheme has two advantages. One is the overhead reduction through eliminating the timestamp in each transmitted data packet. The other is the packet rate reduction by putting multiple audio frames or mixed audio-video frames in a single AVP packet. As a result, the end-to-end media unit delay is reduced while achieving implicit synchronization. Furthermore, AVP provides adaptive quality of service (QoS) by the prioritized packetization scheme. Simulation results are presented to verify the advantages of the AVP protocol.     

Efficient group key management for multi-privileged groups

Multi-privileged group communications containing multiple data streams have been studied in the traditional wired network environment and the Internet. With the rapid development of mobile and wireless networks and in particular mobile ad-hoc networks (MANETs), the traditional Internet has been integrated with mobile and wireless networks to form the mobile Internet. The multi-privileged group communications can be applied to the mobile Internet. Group users can subscribe to different data streams according to their interest and have multiple access privileges with the support of multi-privileged group communications. Security is relatively easy to be guaranteed in traditional groups where all group members have the same privilege. On the other hand, security has been a challenging issue and is very difficult to handle in multi-privileged groups. In this paper, we first introduce some existing rekeying schemes for secure multi-privileged group communications and analyze their advantages and disadvantages. Then, we propose an efficient group key management scheme called ID-based Hierarchical Key Graph Scheme (IDHKGS) for secure multi-privileged group communications. The proposed scheme employs a key graph, on which each node is assigned a unique ID according to access relations between nodes. When a user joins/leaves the group or changes its access privileges, other users in the group can deduce the new keys using one-way function by themselves according to the ID of joining/leaving/changing node on the graph, and thus the proposed scheme can greatly reduce the rekeying overhead.     

软件定义车联网的数据转发机制

针对现有车联网（VANET）中数据转发效率低的问题,提出了软件定义网络（SDN）的数据转发机制。首先,设计了软件定义车联网的分层次网络模型,该模型由局部控制器和车辆组成,实现控制与数据转发分离,具有可扩展性、独行性等特点;其次,设计了车辆路由转发机制,该机制采用动态规划和二分搜索的方法,以实现高效的数据转发;最后,通过仿真验证,对比无线自组网按需平面距离向量路由（AODV）、目的节点序列距离矢量路由（DSDV）、动态源路由（DSR）和最优链路状态路由（OLSR）算法,所提的数据转发机制在传递成功比上提高大约100%,而端到端延迟时间降低大约20%。实验结果表明,软件定义车联网的数据转发机制能够提高路由转发效率、减小延迟。     

Data rate,path length and network contention trade-off in IEEE 802.11s mesh networks: A dynamic data rate selection approach

Most of the commercially available wireless routers are equipped with multi-rate support to adopt physical data rates based on the channel condition fluctuations. The recent studies in multi-rate support have shown that low data rates are more effective when the channel error rate is high. Because of the physical layer modulation and signal decoding issues, low data rates are sustainable for long transmission ranges. Therefore, for multi-hop mesh networks, low data rates may scale down the end-to-end path length towards the destination in terms of number of hops, resulting in less end-to-end forwarding delay. However, for a network with high traffic load, long transmission ranges may increase contention for channel access among the contending neighbors. This paper uses the diffusion approximation method of queuing analysis to study the trade-off among data rate, end-to-end path length and network contention in a multi-rate mesh network built over the IEEE 802.11s specifications. From the observations of the theoretical analysis, a distributed and localized rate adaptation scheme is proposed for IEEE 802.11s mesh networks, by augmenting the standard peer selection, channel access and forwarding protocols. The performance of the proposed rate adaptation protocol is evaluated and compared with existing rate adaptation protocols using simulation results.     

一种高效可靠的移动Agent间通信机制

作为未来分布式系统的一种主流计算模式,移动Agent技术具有广阔的研究前景.协作与通信是移动Agent系统必不可少的组成部分.然而由于Agent的移动性和自主性,现有研究工作所提出的移动Agent间通信机制在可靠性尤其是有效性上存在着一定的不足,如不能够在底层理想地解决通信失效等问题.针对上述问题,设计了一种具有高度自适应性的消息传递机制--EMFS(efficiently message forwarding scheme).该协议在Agent寻址上采取指针寻址和集中式寻址相结合的方式;而对于通信失效的解决则采用了以检测法为主,辅以同步的方法,从而能够在彻底解决通信失效的基础上,较大地提高整个通信系统的性能.此外还对协议的主要参数进行了讨论,从理论上分析比较了EMFS的性能,并给出了模拟实验数据,说明了协议的正确性和高效性.     

Moset: An anonymous remote mobile cluster computing paradigm

The advance of technology in terms of cellular communications and the increasing computing power of the mobile systems have made it convenient for people to use more of mobile systems rather than static systems. This has seen more of mobile devices in personal and distributed computing, thus making the computing power ubiquitous. The combination of wireless communication and cluster computing in many applications has led to the integration of these two technologies to emerge as Mobile Cluster Computing (MCC) paradigm. This has made parallel computing feasible on mobile clusters, by making use of the idle processing power of the static and mobile nodes that form the cluster. To realize such a system for parallel computing, various issues such as connectivity, architecture and operating system heterogeneities, timeliness issues, load fluctuations on machines, machine availability variations and failures in workstations and network connectivities need to be handled. Moset, an Anonymous Remote Mobile Cluster Computing (ARMCC) paradigm is being proposed to handle these issues. Moset provides transparency to mobility of nodes, distribution of computing resources and heterogeneity of wired and wireless networks. The model has been verified and validated by implementing a distributed image-rendering algorithm over a simulated mobile cluster model.     

Impact of a simple load balancing approach and an incentive-based scheme on MANET performance

Most reactive mobile ad hoc network (MANET) routing protocols such as AODV and DSR do not perform search for new routes until the network topology changes. But, low node mobility does not affect the MANET connectivity and the same routes may be used for a long time. This may cause concentration of traffic on few mobile stations (MSs), which results in congestion and hence longer end-to-end delay. In addition, continuous use of MSs may cause their battery power to get exhausted rapidly. Expiration of MS energy causes disruption of connections traversing through the MSs and could generate many simultaneous new routing requests. Therefore, we propose a load balancing approach called Simple Load Balancing Approach (SLBA), which can be transparently added to any current reactive routing protocol such as AODV and DSR. SLBA minimizes the traffic concentration by allowing each MS to drop RREQ or to give up packet forwarding depending on its own traffic load. Meanwhile, MSs may deliberately give up forwarding packets to save their own energy. For encouraging MSs to volunteer in forwarding packets, we introduce a reward scheme for packet forwarding, named Protocol-Independent Fairness Algorithm (PIFA). We compare the performance of AODV and DSR with and without SLBA and PIFA. Simulation results indicate that SLBA can distribute traffic very well and improve the MANET performance. PIFA is also observed to prevent MANET partitioning and any performance degradation due to selfish nodes.     

Efficient Data Reporting in Intelligent Transportation Systems

Recently, intelligent transportation systems (ITSs) have emerged. These systems can improve traditional transportation systems and provide traffic information to travelers. In the area of transportation, wireless sensor networks (WSNs) can replace the existing wired sensors and expensive traffic monitoring systems to mitigate the time and costs of installing such systems. However, accurate and on-time traffic information delivery is a major challenge, considering the energy constraints of sensor nodes. In this paper, we propose a two-tier architecture that includes a network of mobile objects (vehicles) in the upper layer and a hierarchical WSN in the bottom layer. Using this approach, a portion of loads on the low-power static sensor nodes can be transferred to mobile objects, such as powerful mobile devices. Moreover, to provide accurate and timely traffic information, a QoS-aware link cost function has been proposed and used for data transmission between the static sensor nodes. In addition, due to the mobility of the objects and the probability of losing packets in the mobile object tier, a reliable data forwarding mechanism has been proposed for this tier. In this mechanism, data packets are forwarded to the neighbors, which enhance the probability of the packets’ being received. The performance evaluation results indicate the effectiveness of the proposed architecture and data reporting mechanism for use in ITS applications.     

Increasing autonomy of UAVs

Unmanned aerial vehicles (UAVs) are acquiring an increased level of autonomy as more complexmission scenarios are envisioned [1]. For example, UAVs are being used for intelligence, surveillance, and reconnaissance missions as well as to assist humans in the detection and localization of wildfires [2], tracking of moving vehicles along roads [3], [4], and performing border patrol missions [5]. A critical component for networks of autonomous vehicles is the ability to detect and localize targets of interest in a dynamic and unknown environment. The success of these missions hinges on the ability of the algorithms to appropriately handle the uncertainty in the information of the dynamic environment and the ability to cope with the potentially large amounts of communicated data that will need to be broadcast to synchronize information across networks of vehicles. Because of their relative simplicity, centralized mission management algorithms have previously been developed to create a conflict-free task assignment (TA) across all vehicles. However, these algorithms are often slow to react to changes in the fleet and environment and require high bandwidth communication to ensure a consistent situational awareness (SA) from distributed sensors and also to transmit detailed plans back to those sensors.     

基于3G的移动销售终端的设计及实现

该文基于运行商提供的3G VPDN服务支持,在网点销售终端系统的基础上与第三方数据加密公司合作开发设计适用于除现金业务不能办理的移动销售终端系统,此设计方案着重介绍通信中加密防范措施。     

Termination detection protocols for mobile distributed systems

This paper studies a fundamental problem, the termination detection problem, in distributed systems. Under a wireless network environment, we show how to handle the host mobility and disconnection problems. In particular, when some distributed processes are temporarily disconnected, we show how to capture a weakly terminated state where silence has been reached only by those currently connected processes. A user may desire to know such a state to tell whether the mobile distributed system is still running or is silent because some processes are disconnected. Our protocol tries to exploit the network hierarchy by combining two existing protocols together. It employs the weight-throwing scheme on the wired network side, and the diffusion-based scheme on each wireless cell. Such a hybrid protocol can better pave the gaps of computation and communication capability between static and mobile hosts, thus more scalable to larger distributed systems. Analysis and simulation results are also presented     

Contention-based forwarding with multi-hop connectivity awareness in vehicular ad-hoc networks

Recent vehicular routing proposals use real-time road traffic density estimates to dynamically select forwarding paths. Estimating the traffic density in vehicular ad hoc networks requires the transmission of additional dedicated messages increasing the communications load. These proposals are generally based on unicast sender-based forwarding schemes. The greedy nature of sender-based forwarding can result in the selection of forwarders with weak radio links that might compromise the end-to-end performance. To overcome these limitations, this paper presents TOPOCBF, a novel contention-based broadcast forwarding protocol that dynamically selects forwarding paths based on their capability to route packets between anchor points. Such capability is estimated by means of a multi-hop connectivity metric. The obtained results demonstrate that TOPOCBF can provide good packet delivery ratios while reducing the communications load compared to unicast sender-based forwarding schemes using road traffic density estimates.     

Distributed multi-hop cooperative communication in dense wireless sensor networks

In this paper, we investigate the use of cooperative communications for high performance data dissemination in dense wireless sensor networks. We first identify the limitations of existing cooperative schemes. While we previously proposed a multi-hop cooperative data dissemination scheme, REER, to address these limitations, the construction of such structure relies on a pre-established reference path. The partially centralized approach makes REER unscalable when encountering network dynamics. To address this issue, this paper proposes a novel distributed multi-hop cooperative communication scheme (DMC), which is fully distributed and consists of two operation phases: (1) cooperative mesh structure (CMS) construction, and (2) CMS-based data dissemination, which includes random value-based scheme and distance-based scheme for forwarding node selection. Simulation results show that DMC performs well in terms of a number of QoS metrics, and fits well in large-scale networks and highly dynamic environments.